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Path search and path selection

In the dynamic assignment, several paths are mostly found for an OD pair that a vehicle can take. The decision for one of the paths found via path selection is based on the generalized costs of the paths. The generalized costs consist of the travel time, distance, and link costs (General cost, travel distances and financial cost in the path selection).

The distribution of demand data to the paths can be done according to the following distribution models:

• Use volume (old): Base path search exclusively on volumes of previous simulation runs. These may stem from a previous simulation run or an ANM import.
• Stochastic assignment (Kirchhoff): The distribution is carried out in each iteration according to Kirchhoff based on the smoothed generalized costs of the previous iteration. Less vehicles use paths with higher costs than paths with lower costs. Paths with the same cost get the same volume, regardless of their capacity. The result of the assignment is the following distribution to the paths:
• Paths with higher volumes have lower costs
• Paths with lower volumes have higher costs
• Paths with identical volumes have identical costs
• Equilibrium assignment: Redistributes demand across paths proportionally to costs, from expensive to inexpensive paths, for each OD pair in each iteration: The volume of paths that are more expensive than the average is reduced. The height of the specified volume is proportional to the additional costs of the path. All paths that are cheaper than the average path costs are assigned additional volume. The additional volume is proportional to the cost saving compared with the average path costs (Method of path selection with or without path search). The result of the assignment are identical generalized costs on all paths of a parking lot OD pair, possibly with very different volumes, dependent on the respective capacity of the path.

Choose whether you want path selection to be based on the travel time measured on paths or on the total of travel times on edges. In doing so, you define the calculation of generalized costs. The desired method of cost calculation can be selected in the parameters of dynamic assignment Cost for path distribution with Kirchhoff: (Attributes for calculating costs as a basis for path selection).